Chlorine dioxide is primarily used in pulp bleaching, but there is a growing interest of using it also in other applications such as water purification, fat bleaching or removal of phenol from industrial wastes. Since chlorine dioxide is not storage stable it must be produced on-site.
Production of chlorine dioxide in large scale is usually performed by reacting alkali metal chlorate or chloric acid with a reducing agent such as chloride ions, methanol or hydrogen peroxide at subatmospheric pressure, as described in, for example, EP patent 445493, U.S. Pat. Nos. 5,091,166 and 5,091,167. These production methods are highly efficient but are only suitable for production in large scale, for example at pulp mills consuming considerable amounts of chlorine dioxide for bleaching. In small scale applications, for example water purification, the chlorine dioxide is generally produced by reacting sodium chlorite with an acid.
EP patent 612686 disclose production of chlorine dioxide from alkali metal chlorate and hydrogen peroxide at substantially atmospheric pressure.
U.S. Pat. No. 5,376,350 discloses a method of producing chlorine dioxide from chlorate ions and a reducing agent in a plug flow reactor which is suitable for production in small scale. Although the method works well it is still desirable to further improve the efficiency.